Servo-trigger mechanisms for automatic firearms of the open breech type



March 23, 1965 B. MAILLARD 3,174,400

SERVO-TRIGGER MECHANISMS FOR AUTOMATIC FIREARMS OF THE OPEN BREECH TYPE Filed Nov. 26, 1962 5 Sheets-Sheet 1 IIIIIIII March 23, 1965 B. MAILLARD 3,174,400

SERVO-TRIGGER MECHANISMS FOR AUTOMATIC FIREARMS OF THE OPEN BREECH TYPE 5 Sheets-Sheet 2 Filed Nov. 26, 1962 March 23, 1965 a. MAILLARD SERVOTRIGGER MECHANISMS FOR AUTOMATIC FIREARMS OF THE OPEN BREECH TYPE 5 Sheets-Sheet 3 Filed Nov. 26, 1962 Fig.6

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:IIIIIIIIIIIIIIIIIIII IIIIIIIIIIIIII/IIII/I/IIII/IIIIIIIIIIIIII/IIII%Q IIIIIII 7IIIII/I/II/I/IIII/IIIIII March 23, 1965 a. MAILLARD 3,

SERVO-TRIGGER MECHANISMS FOR AUTOMATIC FIREARMS OF THE OPEN BREECH TYPE 5 Sheets-Sheet 4 Filed Nov. 26. 1962 .97 23 I A 24 V 32 22 fin-1 Q 1 40 March 23, 165 B. MAILLARD 3,174,40

SERVO-TRIGGER MECHANISMS FOR AUTOMATIC FIREARMS OF THE OPEN BREECH TYPE Filed Nov. 26. 1962 5 Sheets-Sheet 5 United States Patent Ofifice 3,174,406 Patented Mar. 23, 1965 4 Claims. Eel. 89-149) The present invention relates to servo-trigger mechanisms for automatic firearms of the open breech type, i.e. to firearms which, immediately before firing, have their breechblock held in the open position against the action of a return spring, by a sear system which must be released to permit closing of the breechblock, first causing a cartridge to be introduced into the cartridge chamber of the firearm and then, after the end of the closing stroke, igniting said cartridge.

The present invention is more especially concerned, among these mechanisms, with those intended for heavy machine guns and automatic guns of this type.

It has already been proposed, in order to spare the firer the effort of operating the trigger, to make use of a servo-mechanism making use of the energy previously accumulated in a resilient system such as a spring, this energy being subsequently released, to fire a cartridge, at the cost of an effort smaller than that which would have been required for directly operating the trigger. But such mechanisms requested from the firer a supplementary operation in order to ensure the accumulation in advance of the energy which is to operate the sear.

The chief object of the present invention is to obviate this drawback while making servo-trigger mechanisms such that they answer better than up to the present time to the various requirements of practice.

According to the present invention, such mechanisms are arranged in such manner that the energy to be brought into play for releasing the breechblock, when the firer operates the trigger, is supplied by that accumulated in the return spring of the gun when the breechblock is held in open position.

Preferred embodiments of the invention will be hereinafter described with reference to the appended drawings, given merely by way of example, and in which:

FIGS. 1 to 3 diagrammatically show, in three different steps of its operation a servo-trigger mechanism made according to a first embodiment of the invention;

FIGS. 4 and 5 diagrammatically show, respectively in two different positions of its operation, a servo-trigger mechanism made according to a second embodiment of the invention;

FIGS. 6 to 8 show the trigger system, without servotrigger means, of a gun described in a prior patent application and to which the present invention is to be applied;

FIG. 9 shows how the rear portion of the gun of FIGS. 6 to 8 is to be modified so that the invention can be applied thereto;

Finally FIGS. 10 to 12 diagrammatically show, in three different positions of operation, a servo-trigger mechanism made according to a third embodiment of the invention as applied to a gun of the type illustrated by FIGS 6 to 8.

The gun shown by the drawings comprises a breechblock I pushed in the frontward direction by a return spring 2 and sliding in a breechblock body 3.

According to a first embodiment of the invention, illustrated by FIGS. 1 to 3 inclusive, return spring 2, instead of hearing at the rear against the rear end of the breechblock body 3 bears against a sliding member 4 which is urged toward the front by a pulling spring 5.

It will be supposed in what follows:

On the one hand that return spring 2 is such that it exerts, when it is compressed, a thrust of 50 kgs. and when it is expanded a thrust of 15 kgs. for a stroke of the breechblcck of 300 mm;

And on the other hand that spring 5 exerts a maximum pull of kgs. and a minimum pull of 18 kgs.

FIGS. 1 to 3 diagrammatically show sliding member 4 provided with a sliding rod 6 extending in the rearward direction through the rear wall of body 3, which rod 6 tends to be moved by spring 5 toward the front, i.e. toward the left on the drawings.

Rod 6 is provided at the rear end thereof with a projection '7 cooperating with an auxiliary sear 8 which, when lowered, prevents rod 6 from moving rearwardly, thus locking member 4 in a forward position, whereas when, spring 2 being compressed to its maximum value, said sear 8 is lifted, it releases rod 6 which can then move rearwardly until member 4 is given an abutted position at the rear under the effect of the preponderating thrust exerted by return spring 2 and against the thrust exerted by spring 5.

It will be supposed in what follows that the displacement of member 4, between its frontmost position and its rearmost position is only 12 mm.

It will then suffice to connect in a suitable manner (as shown for instance by FIGS. 1 to 3) by a rod 9 which can be shortened against the action of a compression spring 10, member 4 with main sear 11 to obtain a mechanism which works as follows:

When the breechblock of the gun is in the closing position, spring 5 the action of which is then preponderating since it exerts a pull of 18 kgs. whereas the thrust of return spring 2 is only about 15 kgs., keeps member 4 in its forward position (FIG. 1) against an abutment (not shown).

When the mechanism is being set, breechblock 1 is moved rearwardly, compressing return spring 2, without member 4 being able to move backward since it is held by the engagement of sear 8 with projection 7. Return spring 2 is compressed to 50 kgs. and the main sear 11 holds breechblock 1 in its rear position (FIG. 2).

Finally, when (FIG. 3) the firer disengages auxiliary sear 8, since the thrust p1 exerted in the rearward direction by return spring 2 on member 4 then averages 50 kgs., whereas the thrust p2 exerted in the frontward direction by spring 5 is only about 20 kgs., member 4 moves backwards under the effect of a force of about kgs. causing, owing to its connection (ensured through rod 9) with the main sear 11 of the gun, the lifting of this sear, whereby breechblock 1 is sent toward the front by the extension of return spring 2.

This last mentioned spring then expands until it exerts only a thrust of about 15 kgs., i.e. lower than that (of opposed direction and which decreases from 20 to 18 kgs.) then exerted by spring 5. Consequently member 4 returns into its forward position and projection 7 engages sear 8.

It will be understood that in this way if care is taken that the difference between the thrusts of opposed directions pl and p2, at the time when breechblock 1 is held in its opened position, is both great enough to actuate the main sear 11 and low enough to prevent the effort to be exerted to operate auxiliary sear 8 from exceeding the maximum which has been set, the mechanism will comply with the desired purpose.

According to a second embodiment of the invention (FIGS. 4 and 5 where the reference numerals lower than 12 designate parts equivalent to those designated by the same figures in FIGS. 1 to 3), instead of disposing the release member consisting of sliding member 4 quite at the rear of return spring 2, it is disposed at an intermediate point located closer to the front end than to the rear end thereof and said member 4 directly carries the projection 7 intended to cooperate with auxiliary sear 8, breechblock 1 still carrying the projection intended to cooperate with the main sear 11.

Member 4 is then disposed at the desired place on the return spring so that, when said spring, after having been fully compressed (FIG. 4), begins to expand, projection 7, carried by member 4, is engaged by auxiliary sear 8 before breechblock 1 is itself stopped by the main sear 11.

Thus, at the time the breechblock is engaged, the front portion of the return spring, located between member 4 and the breechblock is less compressed than the rear portion of said spring located between said member 4- and the rear fixed abutment 12 against which the rear end of said return spring is bearing.

It is the difference between these compressions which constitutes the effort supported by auxiliary sear 8 and this eifort must of course be sufiicient in order that when it is free to exert its action (by disengagement of said sear 8), it suflices to ensure the disengagement of the main sear 11, to which member 4 is connected through any suitable link means. for instance that shown by FIG. and according to which a projection 13 carried laterally by member 4 is adapted, when said member is released by auxiliary sear 3, to cause retraction of the main sear 11 by pushing back toward the front a retractable finger 14 carried by said sear 11. This finger 14 must be retractable in order to enable, when the breechblock 1 is moving back rearwardly, projection 13 to pass from the front to the rear of said finger.

In one (FIGS. 1 to 3) and the other (FIGS. 4 to 5) of these cases, it may be stated that the action of the energy to be collected from that accumultaed in the return spring of the firearm when the breechblock in the opened position is caught by sear 11 is started by an auxiliary sear 8 releasing a starting member (member 4) urged in one direction by a thrust supplied by return spring 2 and, in the opposed direction, by a smaller resilient thrust.

I will now describe an embodiment of the present invention where it is applied to a firearm of the type described in my prior patent application Ser. No. 198,195 filed May 28, 1962 for Improvements in Automatic Firearms With Recording Barrel, and in Particular in Heavy Machine Guns.

In order to permit a good understanding of the present invention, FIGS. 6. 7 and 8 are reproductions of FIGS. lb, 2b and 4b of said prior patent application, respectively, but with difierent reference numerals.

The structure and operation of the firearm mechanism shown by these figures of said prior application will now be described, to permit of understanding how the present invention can be applied (as shown by FIGS. 9 to 12) to such a mechanism.

in this firearm, the breechblock body 1, pushed toward the front by return spring 2, is held in rear position by two sears 11 located on either side respectively of said breechblock body 1. Said body 1, at the end of every rearward stroke thereof, comes to strike a buffer spring 15.

In order to release breechblock body 1 from the sears 11 by which it is held, a Wedge 16 is provided to move the rear end of each sear 11 toward the middle longitudinal plane of the gun. These two wedges 16 are carried respectively by the lower ends of the branches of a piece 17 in the form of an inverted U disposed astride a sleeve 18 carried by a rear extension of the gun casing 3 coaxially therewith. This piece 17 is pivoted in said rear extension about a transverse horizontal pin 17a extending above said sleeve 18. Piece 17 is urged by springs 19 in the anticlockwise direction toward the position where wedges 16 are not acting on the rear ends of sears 11.

This piece 17 is adapted to be acted upon, near the end of each of its branches and through pins 26 located upproximately at the level of wedges 16, by a dilferential lever 21, also in the form of an inverted U, disposed astride sleeve 18, at the rear of piece 17.

This lever 21 is urged rearwardly by piece 17 transmitting, through pins 26, the force exerted by springs 19. The top portion of this lever 21 is held in the notch 22 of a release lever 24, pivoted in casing extension 3 about transverse pin 17a and which will be more explicitly referred to hereinafter.

The lower ends of the branches of said lever 21 are connected to a trigger mechanism actuated directly by the gunner.

The whole is arranged in such manner that, when the gunner depresses the trigger, he causes lever 21, the top of which is held by notch 22, to pivot in the clockwise direction thus causing, through pins 20, piece 17 to pivot about pin 17a, so that the wedges 16 carried by said piece 17 are moved toward the front.

In the above description of the structure and operation of the fire control mechanism disclosed in said prior patent application, lever 21 pivots about its top portion held imposition by the notch 22 of lever 24. This lever 24 is retracted when the last cartridge of the belt has left its introduction position, whereby firing is automati- Cally stopped after this last cartridge has been fired, breechblock body 1 remaining held in its rearmost position. This is due to the fact that the top portion of lever 21 is then allowed to move rearwardly, together with pins 26 and wedges 16, which are pushed back in the rearward direction by springs 19. Sears 11 then come back into hooking position and hold breechblock body 1 in its rear position after the last cartridge has been fired. It is thus possible to resume firing immediately by introducing a fresh cartridge belt into the belt feed mechanism without having to cock the gun before firing.

The device for retracting lever 24, with its notch 22, after the last round has been fired is made as follows in said prior patent application.

When the last cartridge of a belt leaves its introduction position to be introduced into the cartridge chamber of the firearm, a push-piece 23 (FIGS. 7 and 8) is retracted (i.e. moved toward the left) against the action of a return spring 27.

This push-piece 23 passes above the top of U-shaped piece 17, to act, through its rear edge, as an abutment cooperating with release lever 24 in which notch 22 is formed.

The system is arranged in such manner that, when push-piece 23 is left free to move toward the front, release lever 24 which, up to then, was maintained by said push-piece 23 in a position such that notch 22 formed an abutment for the upper part of lever 21, as above indicated, swings in the anti-clockwise direction under the effect of springs 19 acting through piece 17 so that notch 22 releases the top portion of lever 21, which then moves toward the rear, together with wedges 16, so that sears 11 are free to return into their active positions. Said sears then catch and hold breechblock body 1 in its rear position (open position).

In the above mentioned prior patent application the mechanism which has just been described is operated through direct trigger means.

According to the present invention such a mechanism is operated through a trigger system which will now be described with reference to FIGS. 9 to 12.

it should be noted that, in FIGS. 10 to 12, for the sake of simplification, the trigger system is shown as being spread along a plane, the elements that play the same part as those illustrated by FIGS. 6 to 8 being designated by the same reference numerals respectively. For instance the wedges 16 of FIGS. 6 to 8, which act transversely on the rear ends of sears 11, which oscillate in a plane perpendicular to that of FIG. 8, are replaced by cams 16 acting directly upon the rear ends of sears 11, which oscillate in the very plane of FIGS. to 12.

FIG. 9 shows how, in an embodiment of the present invention, the rear end of return spring 2 is supported in a firearm similar to that of FIGS. 6 to 8.

Instead of having this rear end of spring 2 merely applied against the rear wall of back block 3, as in the construction of FIGS. 6 to 8, this rear end bears against a flange 25 provided at the rear end of a sleeve 26 mounted sl-idable about buffer spring and extending inside return spring 2. Said rear end of sleeve 26 is operative-1y connected with a system forming the equivalent of the auxiliary sear 8 of FIGS. 1 to 3 as it will be hereinafter explained with reference to FIGS. 10 to 12.

As it is known, when breechblock 1 is nearing the end of its rearward, or recoil, stroke, its rear edge 29 comes to strike an abutment 28 carried by the front end of buffer spring 15. As a matter of fact, FIG. 9 shows the position of the parts of the system at the end of a rearward stroke of breechblock 1. Buffer spring 15 is then compressed, after which it expands and launches back breechblock 1 in the forward direction.

The rear flange of sleeve 26, which corresponds to the sliding member 4 of FIGS. 1 to 3, carries a projection 30.

Two link systems are provided, one between said projection and an intermediate point of differential lever 21 and the other between the lower end of said differential lever 21 and the trigger member proper.

The first of these link systems is made as follows (FIGS. 10-12):

A primary lever, which comprises a downward branch 31 and a forward branch 32 is pivoted to the framework or casing of the firearm about an axis 33. The end of the downward branch 31 extends behind projection 36', with which it is kept in contact because said projection 30 is pushed toward the rear by return spring 2 whereas another spring 5 urges said branch 31 of the primary lever toward the front.

A secondary lever which comprises two branches 34 and 35 is pivoted to the framework of the firearm about an axis as located at the same level as axis 33, forwardly thereof. Branch 34 is substantially horizontal, extending toward the rear so that its end part passes under the end of the forward branch 32 of the primary lever. The second branch 35 of the secondary lever extends downwardly and has an intermediate point 37 thereof (located at about mid-height) connected through a link 38 with a point 39 of the rear end of piece 17, which plays the same part as the inverted U-shaped piece 17 of FIGS. 6 to 8. Point 39 is close to the pivot pin 20 through which piece 17 is pivotally connected to differential lever 21, equivalent to that above described with reference to FIGS. 6 to 8.

The above mentioned .spring 5 extends between the downward branches 31 and 35 of the primary and secondary levers respectively.

The second of the above mentioned link systems, which connects the lower end of differential lever 21 with the trigger member proper, is made as follows.

A link 40 connects the lower end of differential lever 21 with the upper end of the top branch 41 of a control lever pivoted to the framework of .the firearm about an axis 42 located under differential lever 21. The lower branch 43 of said control lever, which is longer than its top branch 41 and which is urged in the clockwise direction by a spring 44 toward a fixed abutment 45, is adapted to cooperate with a locking member 46 to be referred to hereinafter.

Also pivoted about said axis 42, there is an arm 47, hereinafter called last shot locking member, extending toward the rear and the rear end of which is provided with a notch and is intended to cooperate with the end of the downward branch 35 of the secondary lever.

A spring 48 urges said locking member 47 in the anticlockwise direction so as to tend to bring its rear end toward the end of the downward branch 35 of the secondary lever. The top branch 41 of the control lever carries a projection 49 adapted to cooperate with a pin 50 of locking member 47 to urge it in the clockwise direction, thus compressing spring 48, when control lever 41-43 is itself pivoted in the clockwise direction.

A trigger lever 51, pivoted to the framework of the firearm about an axis 52 and urged upwardly by a spring 53, comprises two arms 54 and 55.

Arm 54 cooperates with the above mentioned locking member 46 (which is pivoted to the framework of the firearm about an axis 55), in such manner that, when the gunner depresses lever 51, said arm 54 pushes locking member 46 away from the position (toward which it is urged by a spring 57) where it acts as a rear abutment for the lower end of the arm 43 of control lever 41-43.

The other arm 55 of trigger lever 51 cooperates with a pawl 58 pivoted to the framework of the firearm and subjected to the action of a spring 59. As long as the gunner depresses trigger lever 51, the arm 55 of this lever permits this spring 59 to keep pawl 53 in the position where it holds the lower branch 43 of control lever 41-43 in its rearmost position (FIGS. 11 and 12) where, as long as push-piece 23 (mentioned with respect to FIGS. 6 to 8) remains pushed toward the right by spring 27, sear 11 is kept out of action and the firearm is firing a burst.

The mechanism diagrammatically illustrated by FIGS. 9-11 works as follows:

In the position of rest, breechblock 1 being in closing position, i.e. in forward position, the parts of the mechanism occupy the position shown by FIG. 10. Spring 5 pulls lever branches 35 and 31 toward each other. The limit position of branch 35 toward the right is determined by abutment 45, through link 38, a portion of piece 17 (between pivot pins 39 and 2G), a portion of lever 21 (between pivot pin 20 and the left hand end of link 40), link 4-0, and lever 41-42 itself applied against said abutment 45. Since, for this relative position of the parts, the force of spring 5 is greater than that of return spring 2, projection 30, carried by the flange 25 of sleeve 26 is pushed in its foremost position, determined by an abutment not shown, by lever branch 31, pulled by spring 5 against the thrust of spring 2. For this position of the parts, piece 17 does not act upon the rear end of sear 11 which is therefore held by its spring in active position. The projection 49 of control lever 41-43 bears against the pin 50 of the last shot locking member 47 so as to hold said member out of contact with the end of the downward branch 35 of the secondary lever 44-45. Trigger lever 51, under the action of its return spring 53 is in inactive position, whereas locking member 46 is in active position. A small clearance exists between said member 46 and the lower end of control lever 41-43.

When breechblock 1 is moved toward the rear for cocking the firearm, return spring 2 is compressed and its thrust upon projection 30 increases gradually until it becomes greater than the force exerted by spring 5. At this time, projection 33 moves very slightly toward the right, pivoting lever 31-32 in the anti-clockwise direction. This movement, transmitted through lever 34-35, link 38, a portion of piece 17 (between pivot pins 39 and 20), a portion of lever 21 (between pivot pin 20 and the left hand end of link 40) and said link 40, causes the lower end of control lever 41-43 to pivot away from abutment 45 and into contact with the trigger locking member 46. The last shot locking member 47, pushed by its spring 48, follows the small angular displacement of lever 41-43 but not sufiiciently to come into engagement with the lower end of the downward branch 35 of the secondary lever 34-35.

Return spring 2 is more and more compressed until breechblock 1 is hooked in rear position by sear 11. The: positions of the elements of the mechanism are then very." close to those shown by FIG. 10, with practically the only difference that the lower end of control lever 41-43 is. resiliently applied against the trigger locking member 46,, said member 46 (which plays the same part as the auxiliary sear 8 of FIGS. 1-3) preventing control lever 41-43 from rotating in the anti-clockwise direction under the effect of the thrust of spring 2 transmitted thereto through. the parts above mentioned.

In order to fire a burst, trigger lever 51 is fully depressed so that the arm 54 of this lever pushes locking member 46 away from the path of travel of the lower endi of lever 41-43, which is then free to move in the anti-- clockwise direction. The thrust of return spring 2 is; then allowed to move several parts which, up to then, were prevented from moving by their connection with control lever 41-43 previously blocked by locking member 46 in the position of FIG. 10. The movements that. take place are as follows:

Projection 30, carried by flange 25, is pushed toward the rear (i.e. toward the right) by return spring 2.

This causes lever 31-32 to pivot in the anti-clockwise direction and to transmit to lever 34-35 a pivoting displacement in the clockwise direction.

Lever branch 35 pushes, through link 33, piece 17 which pivots in the clockwise direction and acts upon sear 11 to move it into inoperative position, thus releasing breechblock 1, which is launched toward the front (i.e. toward the right) by return spring 2. The position then occupied by the parts, which is that shown in solid lines by FIG. 11, corresponds to that illustrated by FIG- 3 in the case of a simplified construction.

On the other hand, as soon as trigger lever 51 was.

depressed, its arm 55 released pawl 58 which, under the action of its spring 59, pivoted in the clockwise direction so as to be able to cooperate with the lower end of lever 41-43, thus held by said pawl in the position shown by, FIG. 11 as long as trigger lever 51 is depressed.

Since lever 41-43 is thus fixed and since the top end of differential lever 21 is fixed by its engagement with the notch 22 of lever 24, pivot pin is fixed and piece 17' is also fixed, thus keeping sear 11 in inoperative position. Automatic firing of the gun therefore takes place as long: as trigger lever 51 is kept in its depressed position.

At the end of every forward stroke of breechblock 1, the force of spring 5 once more becomes greater than that of spring 2 and flange is moved toward the front by the action on its projection 39 of lever 31-32 pivoted in the clockwise direction by spring 5 (position shown in dotted lines in FIG. 11). But lever 34-35 is not moved.

Upon every shot being fired, breechblock 1 recoils and spring 2 is again compressed. The force of this spring 2 once more becomes greater than that of spring 5 and it pushes back projection toward the right, the parts returning into the position shown in solid lines in FIG. 11.

Then the buffer spring 15 (FIG. 9), overcoming the resistance of return spring 2, launches back breechblock 1 toward the front to fire the next shot.

Automatic firing thus goes on, and stops only when trigger lever 51 is released. Upon being released, said lever 51 pivots in the clockwise direction under the effect of its spring 53 and its arm pushes pawl 58 in the anti-clockwise direction against the action of spring 59. Spring 44 pulls lever branch 43 toward the left, thus causing lever 41-43 to pivot in the clockwise direction until it is again blocked by locking member 46 which has pivoted in the clockwise direction as a consequence of the displacement of the arm 54 of trigger lever 51.

Due to the pivoting of lever 41-43 in the clockwise direction, differential lever 21, the top end of which s held in the notch 22 of lever 2 has pivoted in the anticlockwise direction about said top end thereof. Pivot pin 20 has therefore moved toward the rear, causing piece 17 to turn so as to release sear 11, which is returned into active position by its return spring and catches breechblock 1 on the next passage thereof. The parts have thus been returned into their positions illustrated by FIG. 10.

During the whole time of a burst, primary lever 31-32 therefore oscillates between the two positions shown by FIG. 11, respectively in solid lines and in dotted lines.

In order to fire a single shot it sufiices to depress trigger lever 51 and to release it immediately so that the lower end of lever 41-43 is not caught by pawl 58 and immediately returns to its initial position where it is blocked by lock in member 46. Since piece 17 is then returned into the position of FIG. 10, sear 11 is once more in active position and stops breechblock 1 when it comes back toward the front.

As long as a burst is being fired, the parts remain in the position of FIG. 11, primary lever 31-32 oscillating between the two positions shown by said FIG. 11, respec-- tively in solid lines and in dotted lines.

As long as a cartridge belt is passing through the gun feed mechanism and is feeding cartridges to the gun, push-piece 23 is prevents through means not shown, from moving toward the front (i.e. toward the left in FlGS. iii-l2), despite the efforts exerted thereon in this direction by lever 24, itself acted upon by differential lever 21 the top part of which is engaged in the notch 22 of said lever 24. When the last cartridge of the belt makes its last displacement in the feed mechanism, the means in question temporarily release push-piece 23, which then slides toward the front under the action of said lever 21, which then escapes from notch 22. Under the action of spring 5, which is then stronger than spring 2 and the action of which is transmitted through lever branch 35 and link 33, this lever 21 then swings in the clockwise direction about the pivot pin connecting it to link 4%) and causes piece 17 to move toward the rear and to release sear 11, which is then brought by its return spring into active position, so as to catch breechblock 1 on the next recoil stroke thereof produced by the firing of the last cartridge of the belt.

During this movement, the lower end of the branch 35 of the secondary lever has been engaged by the last shot locking member 4'7, pushed by its spring 48.

The position of the parts is then that illustrated by FIG. 12.

It should be noted that spring 2 then exerts a strong thrust on primary lever 31-32 in the anti-clockwise direction. But since the secondary lever 34-35 is locked by member 47 and control lever 41-43 is locked by pawl 58, piece 17 cannot be moved toward the front.

The gunner then releases trigger lever 51 which, under the action of its spring 53, pivots in the clockwise direction and brings pawl 58 out of cooperating engagement with control lever 41-43. Spring 44 immediately pulls lever 41-43 in the clockwise direction and since, during this movement, secondary lever 34-35 is still prevented from moving by locking member 47, the rotation of control lever 41-43 causes lever 21 to pivot so that its top portion re-engages the notch 22 of lever 24 which has been returned into position by spring 27 acting through push-piece 23.

At the end of this movement the projection 49 of lever 41-43 moves locking member 47 out of engagement with secondary lever 34-35.

The parts have then been returned into the position of FIG. it).

Anyway the servo-trigger mechanism above described has, in addition to the advantages already set forth, that resulting from the fact that, as the trig er can come back into active position only when the compression of return spring 2 has become smaller than the action of spring 5, hooking of the sear always takes place in a complete fashion without it being necessary to provide a special mechanism for this purpose.

in a general manner while the above description discloses what are deemed to be practical and eflicient embodiments of the invention, the present invention is not limited thereto as there might be changes made in the arrangement, disposition and form of the parts without departing from the principle of the invention as comprehended within the scope of the appended claims.

What I claim is:

1. An automatic firearm which comprises, in combination, a barrel provided with a cartridge chamber, a breechblock slidable with respect to said barrel between a cartridge chamber closing position and a rearmost cartridge chamber opening position, a return spring operatively connected with said breechblock for being tension-ed by it during its movement from cartridge chamber closing position toward cartridge chamber opening position, sear means for holding said breechblock in cartridge chamber opening position, said sear means comprising a movable member subjected to the action of said return spring, an auxiliary spring operatively connected with said movable member to act thereon in a direction opposed to that in which said return spring is acting thereon, said two springs being of such arrangement and force that said return spring is preponderating when said breechbiock is in its rearmost cartridge chamber opening position and said auxiliary spring is preponderating when said breechblock is in cartridge chamber closing position, said sear means further comprising a main sear for retaining said breechbiock in its rearmost cartridge chamber opening position, and an auxiliary sear for retaining said movable member in the position thereof corresponding to said breechblock in its rearmost cartridge chamber opening position, a trigger for retracting said auxiliary sear from cooperating engagement with said movable member, and means for operatively connecting said main sear with said movable member, said last mentioned means being arranged to be driven by said movable member, when said member is released by said auxiliary sear, in the direction that disengages said main sear, under the preponderating action of said return spring over said auxiliary spring.

2. A firearm according to claim 1 further comprising a pawl operative by said trigger and operatively connected with said last mentioned means for locking said means in the position corresponding to the disengagement of said main sear as long as said trigger is kept in the position where it retracts said auxiliary sear.

3. An automatic firearm which comprises, in combination, a barrel provided with a cartridge chamber, a breechblock slidable with respect to said barrel between a cartridge chamber closing position and a rearmost cartridge chamber opening position, a cartridge feed mechanism for feeding cartridges to said cartridge chamber, a return spring operatively connected with said breechbloek for being tensioned by it during its movement from cartridge chamber closing position toward cartridge chamber opening position, sear means for holding said breechblock in cartridge chamber opening position said sear rneans comprising a movable member subjected to the action of said return spring, an auxiliary spring operatively connected with said movable member to act thereon in a direction opposed to that in which said return spring is acting thereon, said two springs being of such arrangement and force that said return spring is preponderating when said breechblock is in its rearmost cartridge chamber opening position and said auxiliary spring is preponderating when said breechblock is in cartridge chamber closing position, said sear means further comprising a main sear for retaining said breechblock in its rearmost cartridge chamber opening position, said main sear being capable of occupying either an active position where it retains said breechbloek in its rearmost position era retracted position where it releases said breechblock, said sear means further comprising an auxiliary sear operatively connected with said movable member, for releasably holding it in the position thereof corresponding to said breechblock in its rearmost cartridge chamber opening position, said auxiliary sear having a retracted position in which it releases said auxiliary spring, a trigger operatively connected with said auxiliary sear for moving it into said retracted position, means for operatively connecting said main sear with said movable member, said last mentioned means being arranged to be driven by said movable member, when said member is released by said auxiliary sear, in the direction that disengages said main sear, under the preponderating action of said return spring over said auxiliary spring, means responsive to the presence of cartridges in said firearm feed mechanism for controlling said main sear to hold it in retracted position as long as there are cartridges in said feed mechanism and to bring it into active position when the last cartridge is being fed by said feed mechanism.

4. An automatic firearm which comprises, in combination, a barrel provided with a cartridge chamber, a breechblocl: slidable with respect to said barrel between a cartridge chamber closing position and a cartridge chamber opening position, a return spring operatively connected with said breechblock for being tensioned by it during its movement from cartridge chamber closing position toward cartridge chamber opening position, a retractable sear for holding said breechblock in cartridge chamber opening position, and releasing means for retracting said sear from said breechblock holding position, and means, exclusive of said breechblock, interposed between said return spring and said releasing means, for transmitting to said releasing means, for operation thereof, the energy stored up in said return spring when said breechblock is in cartridge chamber opening position.

References Cited by the Examiner UNITED STATES PATENTS 2,427,304 9/47 Robbins 89-449 BENJAMIN A. BORCHELT, Primary Examiner.. 

1. AN AUTOMATIC FIREARM WHICH COMPRISES, IN COMBINATION, A BARREL PROVIDED WITH A CARTRIDGE CHAMBER, A BREECHBLOCK SLIDABLE WITH RESPECT TO SAID BARREL BETWEEN A CARTRIDGE CHAMBER CLOSING POSITION AND A REARMOST CARTRIDGE CHAMBER OPENING POSITION, A RETURN SPRING OPERATIVELY CONNECTED WITH SAID BREECHBLOCK FOR BEING TENSIONED BY IT DURING ITS MOVEMENT FROM CARTRIDGE CHAMBER CLOSING POSITION TOWARD CARTRIDGE CHAMBER OPENING POSITION, SEAR MEANS FOR HOLDING SAID BREECHBLOCK IN CARTRIDGE CHAMBER OPENING POSITION, SAID SEAR MEANS COMPRISING A MOVABLE MEMBER SUBJECTED TO THE ACTION OF SAID RETURN SPRING, AN AUXILIARY SPRING OPERATIVELY CONNECTED WITH SAID MOVABLE MEMBER TO ACT THEREON IN A DIRECTION OPPOSED TO THAT IN WHICH SAID RETURN SPRING IS ACTING THEREON, SAID TWO SPRINGS BEING OF SUCH ARRANGEMENT AND FORCE THAT SAID RETURN SPRING IS PREPONDERATING WHEN SAID BREECHBLOCK IS IN ITS REARMOST CARTRIDGE CHAMBER OPENING POSITION AND SAID AUXILIARY SPRING IS PREPONDERATING WHEN SAID BREECHBLOCK IS IN CARTRIDGE CHAMBER CLOSING POSITION, SAID SEAR MEANS FURTHER COMPRISING A MAIN SEAR FOR RETAINING SAID BREECHBLOCK IN ITS REARMOST CARTRIDGE CHAMBER OPENING POSITION, AND AN AUXILIARY SEAR FOR RETAINING SAID MOVABLE MEMBER IN THE POSITION THEREOF CORRESPONDING TO SAID BREECHBLOCK IN ITS REARMOST CARTRIDGE CHAMBER OPENING POSITION, A TRIGGER FOR RETRACTING SAID AUXILIARY SEAR FROM COOPERATING ENGAGEMENT WITH SAID MOVABLE MEMBER, AND MEANS FOR OPERATIVELY CONNECTING SAID MAIN SEAR WITH SAID MOVABLE MEMBER, SAID LAST MENTIONED MEANS BEING ARRANGED TO BE DRIVEN BY SAID MOVABLE MEMBER, WHEN SAID MEMBER IS RELEASED BY SAID AUXILIARY SEAR, IN THE DIRECTION THAT DISENGAGES SAID MAIN SEAR, UNDER THE PREPONDERATING ACTION OF SAID RETURN SPRING OVER SAID AUXILIARY SPRING. 